Dispensers of this kind are already known and have been available to consumers for a long time. The piston that drives the product to be ejected translationally is generally mounted at the end of a threaded rod that cooperates with a nut integrally attached to the dispenser. The rod is in turn driven to rotate incrementally via a pushbutton actuated by the user (see French Patent 2 555 471, for example and French Patent Application 88-05026, filed Apr. 15, 1988).
When filling such a dispenser, the part of the dispenser including the drive mechanism is generally kept separate from the reservoir portion. This makes it possible to prevent improper handling during filling, which would make the dispenser unusable and hence unsaleable, since the portion including the drive mechanism has a relatively high production cost. Molding a product inside the reservoir presents no difficulty, since it suffices to close the reservoir with a bottom in order to form a container. However, extruding or compacting a product inside a container often does present problems of feasibility.
If one seeks to extrude a product into a container having a bottom by having the product substantially fit to the inside walls of the container, then when the product drops into the container the air between the container bottom and the product is trapped, and tends to stop the progress of the product toward the container bottom. Despite the several escape routes for the air that may exist through the interstices between the product and the walls of the container (these interstices form in the course of the filling operation and are deleterious to the appearance, as seen from the outside, of the product extruded into the reservoir), a layer of air still remains between the container bottom and the product. In the case where the container bottom corresponds to the piston surface facing the product, the action of the piston on the product is necessarily damped, and its reponse to manual actions by the user on the pushbutton is generally altered. In the case where the product is extruded via the portion of the reservoir opposite its dispensing opening--the piston having been put in place in the reservoir after the reservoir has been filled--and where the dispensing opening is associated with an element that plugs it, in order, along with the reservoir walls, to form a container, the layer of air will prevent the product from filling the reservoir up to the dispensing opening. An empty space of variable size will remain at the level of the dispensing opening, and before he can use the dispenser, the user will necessarily have to actuate the pushbutton several times, to make the product rise in the reservoir. Since the drive mechanism is a slow-feed mechanism, this is somewhat disadvantageous to the salability of the dispenser.
If the product is one that must be compacted inside the reservoir, essentially the same problems are encountered. When the product is compacted by compressing it with a piston onto the bottom of the container, some means of evacuating the air must be provided. If the air is allowed to pass between the walls of the container and the peripheral walls of the compressor piston, then the product is not compacted well at its edges, that is, the surface where it has not been compressed. Contrarily, if the piston is correctly dimensioned, then escape routes for the air must be provided in the container bottom, because the presence of a cushion of air prevents proper compacting of the powder in the vicinity of the cushion, as noted in French patent application 88-02457, filed on Feb. 29, 1988.